Solar water heating: Solar water heaters are simple, reliable, famous and widespread. They are probably the Low Carbon technology closest to being commercially practised. The most efficient designs concentrate solar radiation onto a small diameter tube to maximize heating efficiency. Typically an installation of around 4 m2 is needed for solar hot water, producing sufficient to keep a 200 liter tank topped up. Water heaters can provide all of summer demand and around 50% of current year round demand in an average house, but this could increase to over 60%. It is possible in most efficient settlements, that wood burning stove and solar water heater could provide all heating requirements, both space & water heating.